1, Field of the Invention
This invention relates to novel linear polyester salts and to their use as a matrix material for medicaments that useful in human beings and warm-blooded animals.
2. Description of Prior Art
There are numerous publications that disclose combinations of polymers and drugs designed to give sustained or delayed release of the drugs when these drugs are taken orally. The oral route has as a major drawback when used in conjunction with a sustained release formulation in that body fluids will permeate the polymer part of the formulation in causing swelling and breaking of the protective coating and thus releasing the drug in its entirety. Recently U.S. Pat. No. 3,773,919 disclosed the use of a polylactide in combination with drugs which was then introduced under the skin of a warm-blooded animal to produce a sustained release effect. The polymers used in U.S. Pat. No. 3,773,919 were of a high molecular weight and presented several drawbacks. Namely, the formulation described in this patent produced slow absorption rates in the body, produced formulations of high viscosity which made the admixture of drugs difficult to handle and the high melting points of the admixture made the use of certain heatsensitive drugs impossible. Conversely, low molecular weight polyesters have been tacky semi-solids or syrups, which are difficult to handle. They also have a relatively high acid number which poses problems of tissue irritiation.